The present invention relates to electrical connectors acting as a termination such as a plug or part of a union for a co-axial cable whereby such cable may be connected to a piece of equipment or to another cable having a counterpart connector terminating it.
In the art, the term "coaxial cable" signifies a cable comprising an inner conductor usually of stranded wire, although it may be a single relatively thick inner filament, and an outer conductor, generally in the form of a braided screen sheath concentric with and surrounding said inner conductor, an insulating sheath being interposed between the inner and outer conductors. More particularly the invention relates to such connectors in which an inner contact member, which has resilient fingers to hold the inner conductor of the cable, is held in an insulating body co-axially to an outer contact conductor of the connector, and in which are provided pressure fingers which project into a tapering pressure means and which are capable of being pressed radially inwards against the resilient fingers by means of a pressure member which is displaceable under the axial force exerted by a member used for securing the connector. Hereinafter such connectors will be referred to as "connectors of the kind described".
In a known electric connector of the kind described, the pressure fingers on the insulating body extend axially and on the side nearer the resilient fingers they are so formed that on this side they press uninterruptedly against the particular resilient finger involved for the whole of their length. Further, the free ends of the resilient fingers have on the outside part-conical faces against which is applied a tapering surface in a pressure bush. The pressure bush is urged axially in the direction of the pressure fingers by the axial force exerted by a screw cap which is arranged to be screwed onto the outer sleeve of the connector. In this way the pressure fingers are subjected to a force which operates radially inwards, the effect of which, when the inner conductor of the cable has been inserted, is to press the pressure fingers against the conductor so as to produce electrical contact. In addition, the pressure fingers, which are made of a plastics material, project past the free ends of the resilient fingers on the inner contact member, these free ends having sharp edges at their outer periphery which dig into the pressure fingers.
Since the electrical contact between the resilient fingers and the inner conductor of the cable is generally formed at the free ends of the resilient arms, it happens when the pressure fingers become worn, i.e. when impressions are created in the pressure fingers by the sharp peripheral edges of the resilient fingers, that the electrical contact becomes too small and thus inadequate. Added to this is the fact that the force transmitted from the pressure bush to the pressure fingers is weakened in its capacity as a compressive force on the resilient fingers because it is distributed over the whole area of contact between the spring fingers and the pressure fingers, with the result that the only pressure generated is a relatively weak one distributed over an area which fails to ensure that the inner conductor of the cable is securely clamped under all circumstances, particularly when the pressure fingers are worn and/or the screw cap is not done up sufficiently tightly.
It is an object of the invention to provide a connector of the kind described for co-axial cables whose diameters may vary over a wide range. Further objects include the provision of such a connector which is simple, and cheap to produce, quick to attach to the service device, which can be clamped to the inner conductor of the cables without screwing, and in which a secure electrical contact between the conducting parts of the connector and the conductors of the coaxial cable is always ensured.